The present invention relates to a center buffer coupling for railroad cars with a coupling head and a coupling shaft that holds the coupling head on its front end, the rear end of which is flange-mounted on the frame of the railroad car so that it can swivel horizontally, whereby one section of the coupling shaft is formed of a first partial piece and a second partial piece that are connected to each other by way of an overload safety device.
It is known that with a rigidly supported coupling device, impacts and vibrations that occur during driving (e.g. during braking) can lead to damage to the vehicle and/or to the coupling device itself. To prevent such damage, it is necessary to eliminate the transfer of such impacts, vibrations, etc. This is preferably achieved in that the coupling device is provided with elastic damping means, e.g. draw gears/buffing gears for absorbing such impacts.
These draw gears/buffing gears absorb traction and pressure forces up to a defined magnitude and pass the resulting forces, without damping, over the bearing mount into the vehicle subframe. In this way, each traction and impact force that occurs between the individual car bodies during normal driving operation are absorbed in the impact safety device that is generally designed to be regenerative or destructive when the operating load is exceeded. However, say during impact of the vehicle against an obstacle, it is possible that the energy absorption of the coupling provided is not adequate. This excess impact energy is then transferred directly to the vehicle subframe, which is thereby exposed to extreme stresses. On railroad cars, a case such as this leads to the danger of damage to the vehicle body.
For example, from railroad car technology [handwritten: (DE-36 32 578 A1)] arranging multi-stage energy dissipation devices in the subframe area of railroad cars is known. Generally these have a reversible energy dissipation device as the primary stage, which e.g. is integrated in the coupling shaft of a center buffer coupling in the form of a coupling spring and which will absorb impact forces that occur in driving, maneuvering and coupling operations. The coupling shaft itself can be fastened by way of an articulation and if necessary, by way of breakaway elements on the subframe of the car body.
A second, secondary energy dissipation device for absorbing impact energy resulting from bumping impacts is often mounted in the form of two side buffers on the outer edge of the face side of the respective car body. In this case, the energy dissipation devices are designed such that the conversion of the impact energy resulting from maneuvering accidents is handled in two working stages that change gradually from one to the next, whereby the first stage is integrated in the center buffer coupling and the second stage is mounted upstream of the bearing car body structure.
Another solution [handwritten: DE 3228941 C2] provides that, after the coupling-side energy dissipation device has been fully utilized, the remaining energy is dissipated to the car body-side energy absorbing elements, e.g. friction elements, over a specified breaking point in the coupling link. However, this requires that the final force, at which the coupling connection to the car body is released by the specified breaking point must be very precisely measured, which is also only possible with difficulty with the use of a friction element as well as with specified breaking connections.
The advantage of such a solution, in which during a crash the coupling is released by means of the response of a specified breaking point of the respective car body, lies in the fact that during an accident the greatest possible calculable energy dissipation can be achieved along with a predictable sequence of events, since the center buffer coupling is taken out of the flow of force when a defined force level is exceeded and thus permits the impact of the car bodies and the use of the car body-side energy absorption elements.
As a rule, however, the center buffer coupling is taken out of the force flow, in that the coupling shears off at the specified breaking points such that greater parts of the coupling take up space needed for the movement in reverse in the subframe of the vehicle. In coupling arrangements in which this space is not available, e.g. because of the immediate proximity of a bogie, it becomes impossible to implement the breakaway solution of the clutch in order to take the coupling out of the force flow if a crash occurs.
The present invention is thus based on the object of further developing a center buffer coupling of the type mentioned at the beginning, such that in the case of a crash, i.e. during the occurrence of extreme impact energies, the coupled couplings are shortened in such a way that the energy absorbing elements on the body side dissipates the impact energy transferred between the adjacent car bodies during the impact without additional space being needed behind the coupling in order for the coupling to be taken out of the force flow.
This object is achieved with a center buffer coupling for railroad cars of the type mentioned at the beginning in such a way that the overload security device has a first bolt and at least one second bolt that responds if a specified response force is exceeded in longitudinal and/or transverse direction of the coupling shaft, whereby the first bolt and the at least one second bolt are arranged in succession in axial direction of the coupling shaft.